i really need to start these, but i've been too lazy to learn new form.

for deadlift could i just do 3 singles (after warm ups) at 80% and then add 5 percent a week or something, so after 4 weeks im doing 3 singles at my old max?

i literally just though of this and its probably stupid. i just dont know how to progress. i know 5 reps would be the fastest way, but my form gets terrible after 1 or 2 reps. i dont want to miss out on possible gains, but i also dont want to risk injury.

That sounds like a good way to progress, you could also do the same thing with rest-pause sets, at 80% for 5 reps rest pause and go with the same progression. Just try it out, see how you like it. I think singles or rest pause are the best way to do deadlifts.